I like to think there is no ambiguity regarding dibs in my sales ads. Here is a paragraph from a big sale post I ran last year.
So by failing to post in the thread, you risk losing out to someone who does post in the thread, but does so after your PM. If I happen to be online when your PM comes in, I might post a note in my thread stating that a PM has come in for such and such. If my post beats any other dibs posts, then we can make a deal. If not, the dibs post gets priority.
And with regards to the "multiple lots" part, that doesn't mean I'm going to sit on a dibs for several days (or even several hours) waiting for someone else to buy more. It just means for dibs placed within a short time of each other, typically right after the posting of the sale ad. Or for dibs that post while I'm not logged into the site.
I'm open on dibs with conditions, mainly dibs with a question. I'll consider any post in my sale ad, followed up with a PM to be a placeholder in line until I answer that question. Here is what I said later in that same post I referred to above.
But once your question is answered, I need a firm reply back in short order, or you'll lose your place.
I'm probably an exception though, in that I try to define these sorts of things up front in my sale ads. Most will not go to this much trouble, and that's probably why we have a lot of misunderstandings and disagreements about what "dibs" means. Ultimately, the seller makes the decision as to who they sell to. I just happen to think that the more you define the ground rules in your sale ad, the better. And when you don't define up front how you will deal with dibs vs. questions in the thread vs. PMs, then you are more likely to have a misunderstanding and an upset potential buyer.
